The present invention relates to a robot-teaching cassette by which a robot will be taught to mount a wafer cassette or a substrate cassette on an apparatus for manufacturing a semiconductor or a liquid crystal display device. More specifically, the present invention relates to a robot-teaching cassette which is used to teach a robot to position a cassette on a cassette-supporting base without using the wafer cassette or the substrate cassette.
An example of a conventional robot-teaching method by which a robot will automatically mount a wafer cassette or a substrate cassette on an apparatus for manufacturing a semiconductor or a liquid crystal display device will be described below with reference to FIGS. 8A, 8B and 8C.
The apparatus comprises a cassette-supporting base 1; two cassette-receiving members 2; and a robot 5 including a robot-chucking section 3. Each cassette-receiving member 2 is fixed to the cassette-supporting base 1. The robot-chucking section 3 can be opened and closed by moving its arms 3d horizontally and is fixed to a main body of the robot 5. That is, the robot 5 has a robot arm 5g connected with the chucking section 3 as shown in FIG. 8B and is movable horizontally by a motor of the robot 5. Two cylinders 3e which have piston rods 3f for moving the arms 3d of the chucking section 3 are fixed to an end plate 5h of the robot arm 5g. The piston rods 3f of the cylinders 3e are moved in opposite outward directions to increase the distance between the edges 3b of the arms 3d of the chucking section 3 so that the cassette 4 can be inserted between the edges 3b of the arms 3d. After the insertion of the cassette 4, the piston rods 3f of the cylinders 3 are moved in opposite inward directions to decrease the distance between the edges 3b of the arms 3d until the arms 3d hold the cassette 4 between the edges 3b. The robot arm 5g has four pulleys 5a, 5c, 5d and 5f, a belt 5b extending around the pulleys 5a and 5c, and a belt 5e extending around the pulleys 5d and 5f. The pulley 5d rotates in accordance with the rotation of the pulley 5c. According to the above structure, when an arm shaft 5i connected with a motor shaft of the motor for the robot 5 is rotated by the motor, the belt 5b and the pulley 5c engaged with the belt 5b rotate in accordance with the rotation of the pulley 5a. Then, the pulley 5d rotates together with the pulley 5c to rotate the belt 5e and the pulley 5f. As a result, the chucking section 3 rotates in accordance with the rotation of the robot arm 5g around the arm shaft 5i. That is, even though the robot arm 5g is revolved around the arm shaft 5i by the motor, the pulleys 5a, 5c, 5d, and 5f are rotated to drive the belts 5b and 5e so that the orientation of the arms 3d is not changed, as shown in FIG. 8C.
The method for teaching the robot to mount a cassette 4 on the cassette-supporting base is described below.
The cassette 4 is chucked on the robot-chucking section 3 which is then operated in X, Z, and Y (perpendicular to the sheet of FIG. 8A) directions, and .theta. direction (rotational direction about Z-axis) to place the cassette 4 on the cassette-supporting base 1 as positioned by the cassette-receiving member 2. The positioning of the robot 5 is accomplished by an operator's sense of touch and rough visual observation. The position data thus determined is electronically stored by a control device (not shown in FIGS. 8A and 8B) of the robot 5.
There is a possibility that carrying out the above-described method may damage the cassette 4, the robot-chucking section 3, the cassette-supporting base 1, or the cassette-receiving member 2 because the robot-chucking section 3, the cassette-supporting base 1, and the cassette-receiving member 2 become interlocked with each other via the cassette 4. In addition, because the robot-teaching operation is performed based on the operator's sense of touch and rough visual observation, it is difficult to teach the robot 5, the robot 5 taught in this manner is often not at an accurate position, and the positions of the robot 5 vary according to the operator who taught the robot. Furthermore, the robot-teaching operation takes a long time.